Lighting Strike - Ground Potential Rise - Cable Damage

[SpannerSpark]

Hi all
Called to a neighbour whod had almost direct hit lighting strike, I know this because I witnessed it and the same strike turned my desktop PC and bband modem into charcoal briquettes/paperweights. It also took out her telephone and bband permanently.
All her electrics had tripped but after reset the upstairs lighting and kitchen ring trips wouldnt stay in.
After removing all appliances & lamps and a bit of divide and conquer the only answer left was that one particular cable run in each circuit having a L-cpc short circuit. The lighting was easiest to get at a replace the run and sure enough when the offending cable had its cores stripped out it looks like the cpc had melted at one point melting the live ptfe sleeve, fusing the two copper cores together. I would post an image but dont have the permissions.
Did MW test on the lighting and all ok now. Assume this is the same fault case for the kitchen ring, but the fault is in the fabric of the building and is a floor-up job, so temporarily split it to two 16a radials.
Assume this is ground potential rise, instantaneously melting the cpcs due to fast overcurrent. Assume also that the cpcs went at a weak point, perhaps a nick in the core or manufacturing error.
Firstly has anyone come across this? Secondly I will be recommending a periodic as there is no telling if any other runs/cpcs have been damaged, possibly now not continuous. And thirdly would anyone recommend a new cu, it seems fine (all trips still function and RCD trip times ok), but wonder how stressed it has been.
BTW her system is @15 years old, PME, wiring generally looks in good nick, MCBs in CU with RCD LHS for sockets etc, lighting etc RHS no RCD.
Any advice gratefully received.

 

[richy3333]

Why would a test instrument company (albeit spelt incorrectly) OK the wiring??

 

[DPG]

I think a comma after the 'OK' would make it read better! I think he's saying that even if the megger tests are OK, the wiring may still be weakened. Apologies if I'm putting word into the OP's mouth Daz

 

[SpannerSpark]

I think I agree that a case could be argued for a complete rewire. As a minimum all circuits to be tested for continuity and insulation resistance. The homeowner is getting on to her insurer to see how she stands and what their attitude is. Thanks for all the replies.

 

[trev]

Here's my prediction. The insurers will try their damnedest to get out of paying out a single penny. They'll find some way to do it if they try hard enough, possibly invoking the clause which dictates that the property be kept in good order and regularly maintained. If she hasn't had the wiring checked out previously she could be in trouble.

 

[SpannerSpark]

The house itself is only 15 years old. So I guess to the letter of the recommendations she should have had a periodic 5 years back, like I am certain everyone does.
I do take your point though. I will update this when I get their response.

 

[HappyHippyDad]

If the lightning hit close then prior to the strike their would have been several faint positive streamers and it sounds like one was off your house, it may piggy back the wiring system namely the earth as its usually interlinked and connected throughout the building - the voltages are very large and can do alot of damage even though the positive streamer is not the one to make contact with the actual bolt..... check the link out ...towards the end you can see footage of several streamers a split second before the bolt find its target.

https://www.youtube.com/watch?v=RLWIBrweSU8

That was fascinating! Thanks for posting Darkwood.

 

[Darkwood]

That was fascinating! Thanks for posting Darkwood.

Im a closet nerd as most may have guessed by now I live to soak a lot of this info up in hope to spill it out when the opportunity presents itself... its only in the last decade that this has come to light and even captured ....if you want to mess you mind up more look up lightning sprites and associated displays that shoot out into space off the top of some bolts ..it gives you an added insight into the sheer power of these things.

 

[not clever]

Here's my prediction. The insurers will try their damnedest to get out of paying out a single penny. They'll find some way to do it if they try hard enough, possibly invoking the clause which dictates that the property be kept in good order and regularly maintained. If she hasn't had the wiring checked out previously she could be in trouble.

Bang on Trev, or they will just state it was "an act of God" so un-insurable.

 

[richy3333]

Bang on Trev, or they will just state it was "an act of God" so un-insurable.

But what is the argument if she's an atheist?